1 files changed, 28 insertions, 13 deletions
diff --git a/src/mongo/db/exec/collection_scan.cpp b/src/mongo/db/exec/collection_scan.cpp
index f8550dbe81d..877603a0965 100644
--- a/src/mongo/db/exec/collection_scan.cpp
+++ b/src/mongo/db/exec/collection_scan.cpp
@@ -275,19 +275,36 @@ void CollectionScan::setLatestOplogEntryTimestamp(const Record& record) {
 }
 
 void CollectionScan::assertTsHasNotFallenOffOplog(const Record& record) {
-    // If the first entry we see in the oplog is the replset initialization, then it doesn't matter
-    // if its timestamp is later than the timestamp that should not have fallen off the oplog; no
-    // events earlier can have fallen off this oplog. Otherwise, verify that the timestamp of the
-    // first observed oplog entry is earlier than or equal to timestamp that should not have fallen
-    // off the oplog.
-    auto oplogEntry = uassertStatusOK(repl::OplogEntry::parse(record.data.toBson()));
+    const auto oplogEntry = record.data.toBson();
+    const repl::OplogEntryParserNonStrict oplogEntryParser{oplogEntry};
     invariant(_specificStats.docsTested == 0);
-    const bool isNewRS =
-        oplogEntry.getObject().binaryEqual(BSON("msg" << repl::kInitiatingSetMsg)) &&
-        oplogEntry.getOpType() == repl::OpTypeEnum::kNoop;
+
+    // Indicates that 'oplogEntry' means initialization of a replica set.
+    bool isNewRS{false};
+
+    // Indicates that the timestamp of the observed oplog entry 'oplogEntry' is earlier than or
+    // equal to timestamp that should not have fallen off the oplog.
+    bool tsHasNotFallenOff{false};
+    try {
+        tsHasNotFallenOff =
+            oplogEntryParser.getOpTime().getTimestamp() <= *_params.assertTsHasNotFallenOffOplog;
+
+        // If the first entry we see in the oplog is the replset initialization, then it doesn't
+        // matter if its timestamp is later than the timestamp that should not have fallen off the
+        // oplog; no events earlier can have fallen off this oplog.
+        // NOTE: A change collection can be created at any moment as such it might not have replset
+        // initialization message, as such this case is not fully applicable for the change
+        // collection.
+        isNewRS = oplogEntryParser.getOpType() == repl::OpTypeEnum::kNoop &&
+            oplogEntryParser.getObject().binaryEqual(BSON("msg" << repl::kInitiatingSetMsg));
+    } catch (const AssertionException& exception) {
+        uasserted(8881102,
+                  str::stream() << "Failed to parse the oldest oplog entry" << causedBy(exception));
+    }
     uassert(ErrorCodes::OplogQueryMinTsMissing,
             "Specified timestamp has already fallen off the oplog",
-            isNewRS || oplogEntry.getTimestamp() <= *_params.assertTsHasNotFallenOffOplog);
+            isNewRS || tsHasNotFallenOff);
+
     // We don't need to check this assertion again after we've confirmed the first oplog event.
     _params.assertTsHasNotFallenOffOplog = boost::none;
 }
@@ -431,9 +448,7 @@ void CollectionScan::doReattachToOperationContext() {
 unique_ptr<PlanStageStats> CollectionScan::getStats() {
     // Add a BSON representation of the filter to the stats tree, if there is one.
     if (nullptr != _filter) {
-        BSONObjBuilder bob;
-        _filter->serialize(&bob);
-        _commonStats.filter = bob.obj();
+        _commonStats.filter = _filter->serialize();
     }
 
     unique_ptr<PlanStageStats> ret = std::make_unique<PlanStageStats>(_commonStats, STAGE_COLLSCAN);